Screen Pipe for Thick Oil Thermal Recovery in Horizontal Well Completion

ABSTRACT

A screen pipe, comprises a base pipe with a plurality of oil inlet holes arranged on an outer wall of the base pipe; wherein the screen pipe comprises: a plurality of reinforcing ribs are disposed on an outer circumference wall of the base pipe along an axial direction of the base pipe; a wrap wire is winded at intervals on the plurality of reinforcing ribs along a circumferential direction of the base pipe; and a triangular block shaped foam iron is filled in a space between two adjacent reinforcing ribs of the plurality of reinforcing ribs. When the present invention is in use, the thick oil enters into the gap between the wrap wire and the drive pipe through the wrap wire gap. After filtration by the foam iron, the thick oil enters into the base pipe through the inlet hole, realizing pumping and transportation of the oil.

FIELD OF THE INVENTION

The present invention relates to a screen pipe, and more particularly toa screen pipe for thick oil thermal recovery in horizontal wellcompletion.

BACKGROUND OF THE INVENTION

Oil resources exist in naturally formed oil reservoir, and theexploitation technology varies with different types and inherentcharacteristics of the reservoir. Thick oil, also called heavy oil,refers to heavy crude oil with high viscosity, high density, and highcontents of colloid and asphalt, namely high viscosity heavy crude oil.Generally, the wax content of crude oil is low; therefore, the viscosityof crude oil is high and the flow resistance is large, making itdifficult to recover crude oil.

Thick oil is an important constituent of hydrocarbon energy, and itscharacteristics are as follows: (1) Thick oil contains high levelscontents of colloid and asphalt and low content of light fractions.Meanwhile, the relative density and viscosity of thick oil increase withthe increase in the contents of colloid and asphalt. (2) The viscosityof thick oil is particularly sensitive to temperature. The viscositydecreases sharply with the increase in temperature, and such phenomenonis more significant in crude oil with high viscosity. (3) Thick oilcontains many heteroatoms such as sulfur, oxygen, and nitrogen. (4) Thecontent of paraffin in thick oil is generally low. However, a smallnumber of oilfields are “double-high oil fields” with high contents ofboth asphalt and paraffin, and is characterized by having crude oil withhigh viscosity and high solidifying point. (5) The properties of crudeoil in the same thick oil reservoir often vary greatly between differentwell sections of a vertical oil layer and between different wells on thesame plane.

In China, the reserve of thick oil is rich, and the annual output ofthick oil is accounted for about 10% of the total crude oil output.According to China's second national resource evaluation data, thick oilresources are about 8198.710 tons. However, under stratum temperature,thick oil is too viscous to flow, making it difficult to recovery thickoil by conventional methods. Because thick oil is too viscous and itsmobility ratio over water is too high, the effect of common crude oilrecovery method on thick oil recovery is very limited.

At present, the methods for improving recovery ratios of thick oiladopted in oil fields in China are mainly steam stimulation and steamflooding. However, while the recovery rate of thick oil may be up to 60%after steam stimulation and steam flooding, nearly 40% of thick oil isstill not recovered after the multiple cycles of stimulation and steamflooding. After steam flooding on thick oil reserves, temperature andpressure of the oil layer change significantly, followed by changes inresidual oil saturation between pores and residual oil distribution inthe wells. However, owing to shallow burial and loose cementation of theoil layer, phenomenon such as casing damage, screen pipe damage, packerdamage or sanding tend to occur during the recovery of horizontal wellsand severely affect the recovery of horizontal wells.

BRIEF SUMMARY OF THE INVENTION

Therefore, the present invention provides a screen pipe for thick oilthermal recovery in horizontal well completion, for facilitating therapid recovery of thick oil and avoiding clogging and damage of thescreen pipe.

According to some embodiments of the present invention, a screen pipefor thick oil thermal recovery in horizontal well completion comprises abase pipe with a plurality of oil inlet holes arranged on an outer wallof the base pipe. A plurality of reinforcing ribs are disposed on anouter circumference wall of the base pipe along an axial direction ofthe base pipe; a wrap wire is winded at intervals on the plurality ofreinforcing ribs along a circumferential direction of the base pipe; anda triangular block shaped foam iron is filled in as pace between twoadjacent reinforcing ribs of the plurality of reinforcing ribs. When thepresent invention is in use, the base pipe is placed in the horizontalsection of the horizontal completed well; thick oil enters into the gapbetween the wrap wire and the drive pipe through the wrap wire gap, andenters into the base pipe through the inlet holes after filtration bythe foam iron, realizing pumping and transportation of the oil.

In the prior art, steam flooding technology has been used in therecovery of thick oil. In steam flooding, a steam injection well and aproduction well are set above an oil reservoir; steam is continuouslyinjected into the steam injection well to heat the strata around thewellbore and the crude oil in the strata. A steam zone graduallyexpanding with the injection of steam is formed in the strata near thewellbore. The steam can reduce oil saturation of the steam zone to alower degree, and drive the flowable crude oil (that is, the differencebetween original oil saturation and residual oil saturation) out of thesteam zone. Meanwhile, in the horizontal section of the horizontalcompleted well, the steam moves vigorously toward an updip direction;and as driven by gravity, the heated crude oil moves toward a downdipdirection. With the increase in temperature of the crude oil, oil-waterand gravel mixture in the horizontal section of the horizontal completedwell would boil, causing denudation of the crude oil (by disturbancecaused by boiling of the mixture). In the present invention, theoil-water and solid mixtures begin to enter into a base pipe from thehorizontal section of the horizontal completed well. A wrap wire is afull metal bar and winded at intervals on the plurality of reinforcingribs to form a primary filter unit for solid gravels with large diameterin the oil-water. A foam iron forms a second filter unit for solidgravels with small diameter to realize the purpose of sand control forthe base pipe. Moreover, when change in production pressure of thehorizontal section of the horizontal completed well occurs due to theinfluence of liquid pressure and heat contained in the oil-water, asecond filter zone formed between two adjacent reinforcing ribs of theplurality of reinforcing ribs would be compressed. However, a triangularblock shaped foam iron is filled in the second filter zone; whendeformation of the foam iron occurs under stress, a plurality of flowchannels with irregular geometric shapes would still form in the secondfilter zone to allow the oil-water mixture to pass through. In addition,when stressed, pore channels in the foam iron change slightly, making itdifficult to fully block the pore channels. Meanwhile, as the foam ironhas a certain degree of flexibility, the pore channels in the foam ironwould recover when elastic deformation is restored so that the seepagecapacity of the second filter zone can be maintained to ensuresuccessful recovery of the thick oil.

According to another embodiment of the present invention, the screenpipe for thick oil thermal recovery in horizontal well completionfurther comprises a plurality of strengthening ribs annularly disposedon the wrap wire along the axial direction of the base pipe. In thehorizontal section of the horizontal completed well, the wrap wire ispressured by the oil layer, and the pressure varies constantly with thechange in oil layer temperature. That is, during sudden changes in thepressure, the wrap wire is extremely vulnerable to damage. However, inthe present invention, a plurality of strengthening ribs are annularlydisposed on the wrap wire, providing a stable support for the primaryfilter unit formed by the wrap wire to cope with the constantly changingproduction pressure in the horizontal section of the horizontalcompleted well and extend the service life of the wrap wire.

According to yet another embodiment of the present invention, the outerwall of the wrap wire is coated preferably with TiALN-WC/C coating. Asthe friction coefficient of the TiALN-WC/C coating is only 0.1, theTiALN-WC/C coating can significantly reduce friction loss between thesolids, such as gravel, and the wrap wire when the solids continuouslycontact the wrap wire. Meanwhile, the TiALN-WC/C coating isself-lubricating, greatly ensuring the service life of the wrap wire inthe horizontal completed well.

According to yet another embodiment of the present invention, the basepipe further comprises a connector, wherein each of two ends of the basepipe is connected with a blind pipe through the connector respectively.Preferably, according to the actual needs in oil recovery, the base pipeis connected with the blind pipe though the connector for facilitatingthe pumping and transportation of crude oil. The present inventionabandons direct welding of the blind pipe to the base pipe as adopted inthe conventional art when laying the pipeline so as to facilitate thereplacement of damaged wrap wires without having to replace the basepipe and wrap wire entirely, therefore reducing the production cost inthick oil recovery.

For making the above and other purposes, features and benefits becomemore readily apparent to those ordinarily skilled in the art, thepreferred embodiments and the detailed descriptions with accompanyingdrawings would be put forward in the following descriptions.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention would become more readily apparent to thoseordinarily skilled in the art after reviewing the following detaileddescription and accompanying drawings, in which:

FIG. 1 is a schematic drawing of the screen pipe according to anembodiment of the present invention.

FIG. 2 is a longitudinal cross-section view of the screen pipe accordingto an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention would now be described more specifically withreference to the following embodiments. It is to be noted that thefollowing descriptions of preferred embodiments of this invention arepresented herein for purpose of illustration and description only. It isnot intended to be exhaustive or to be limited to the precise formdisclosed.

In FIG. 1 and FIG. 2, this embodiment comprises a base pipe 4 with aplurality of oil inlet holes 5 arranged on an outer wall of the basepipe 4; wherein a plurality of reinforcing ribs 3 are disposed on anouter circumference wall of the base pipe 4 along an axial direction ofthe base pipe. A wrap wire 2 is winded at intervals on the plurality ofreinforcing ribs 3 along a circumferential direction of the base pipe;and a triangular block shaped foam iron 8 is filled between two adjacentreinforcing ribs of the plurality of reinforcing ribs. When the presentinvention is in use, the base pipe is placed in the horizontal sectionof the horizontal completed well; thick oil enters into the gap betweenthe wrap wire and the drive pipe through the wrap wire gap, and entersinto the base pipe through the inlet holes after filtration by the foamiron, realizing pumping and transportation of the oil.

In the prior art, steam flooding technology has been used in therecovery of thick oil. In steam flooding, a steam injection well and aproduction well are set above an oil reservoir; steam is continuouslyinjected into the steam injection well to heat the strata around thewellbore and the crude oil in the strata. A steam zone graduallyexpanding with the injection of steam is formed in the strata near thewellbore. The steam can reduce oil saturation of the steam zone to alower degree, and drive the flowable crude oil (that is, the differencebetween original oil saturation and residual oil saturation) out of thesteam zone. Meanwhile, in the horizontal section of the horizontalcompleted well, the steam moves vigorously toward an updip direction;and as driven by gravity, the heated crude oil moves toward a downdipdirection. With the increase in temperature of the crude oil, oil-waterand gravel mixture in the horizontal section of the horizontal completedwell would boil, causing denudation of the crude oil (by disturbancecaused by boiling of the mixture). In the present invention, theoil-water and solid mixtures begin to enter into a base pipe 4 from thehorizontal section of the horizontal completed well. A wrap wire 2 is afull metal bar and winded at intervals on the plurality of reinforcingribs 3 to form a primary filter unit for solid gravels with largediameter in the oil-water. A foam iron 8 forms a second filter unit forsolid gravels with small diameter to realize the purpose of sand controlfor the base pipe. Moreover, when change in production pressure of thehorizontal section of the horizontal completed well occurs due to theinfluence of liquid pressure and heat contained in the oil-water, asecond filter zone formed between two adjacent reinforcing ribs 3 of theplurality of reinforcing ribs would be compressed. However, a triangularblock shaped foam iron is filled in the second filter zone; whendeformation of the foam iron 8 occurs under stress, a plurality of flowchannels with irregular geometric shapes would still form in the secondfilter zone to allow the oil-water mixture to pass through. In addition,when stressed, pore channels in the foam iron 8 change slightly, makingit difficult to fully block the pore channels. Meanwhile, as the foamiron has a certain degree of flexibility, the pore channels in the foamiron 8 would recover when elastic deformation is restored so that theseepage capacity of the second filter zone can be maintained to ensuresuccessful recovery of the thick oil.

This embodiment further comprises a plurality of strengthening ribs 1annularly disposed on the wrap wire 2 along the axial direction of thebase pipe 4. In the horizontal section of the horizontal completed well,the wrap wire 2 is pressured by the oil layer, and the pressure variesconstantly with the change in oil layer temperature. That is, duringsudden changes in the pressure, the wrap wire 2 is extremely vulnerableto damage. However, in the present invention, a plurality ofstrengthening ribs are annularly disposed on the wrap wire 2, providinga stable support for the primary filter unit formed by the wrap wire 2to cope with the constantly changing production pressure in thehorizontal section of the horizontal completed well and extend theservice life of the wrap wire.

As a preferred embodiment, the outer wall of the wrap wire 2 is coatedwith TiALN-WC/C coating. As the friction coefficient of the TiALN-WC/Ccoating is only 0.1, the TiALN-WC/C coating can significantly reducefriction loss between the solids, such as gravel, and the wrap wire 2when the solids continuously contact the wrap wire 2. Meanwhile, theTiALN-WC/C coating is self-lubricating, greatly ensuring the servicelife of the wrap wire in the horizontal completed well.

As a preferred embodiment, according to the actual needs in oilrecovery, the base pipe is connected with the blind pipe 7 though theconnector 6 for facilitating the pumping and transportation of crudeoil. The present invention abandons direct welding of the blind pipe 7to the base pipe 4 as adopted in the conventional art when laying thepipeline so as to facilitate the replacement of damaged wrap wires 2without having to replace the base pipe 4 and wrap wire 2 entirely,therefore reducing the production cost in thick oil recovery.

While the invention has been described in terms of what is presentlyconsidered to be the most practical and preferred embodiments, it is tobe understood that the invention needs not be limited to the disclosedembodiment. On the contrary, it is intended to cover variousmodifications and similar arrangements included within the spirit andscope of the appended claims which are to be accorded with the broadestinterpretation so as to encompass all such modifications and similarstructures.

What is claimed is:
 1. A screen pipe for thick oil thermal recovery inhorizontal well completion, comprising a base pipe with a plurality ofoil inlet holes arranged on an outer wall of the base pipe, wherein thescreen pipe comprises: a plurality of reinforcing ribs, disposed on anouter circumference wall of the base pipe along an axial direction ofthe base pipe; a wrap wire, winded at intervals on the plurality ofreinforcing ribs along a circumferential direction of the base pipe; anda triangular block shaped foam iron, filled in as pace between twoadjacent reinforcing ribs, of the plurality of reinforcing ribs.
 2. Thescreen pipe for thick oil thermal recovery in horizontal well completionaccording to claim 1, wherein further comprising: a plurality ofstrengthening ribs annularly disposed on the wrap wire along the axialdirection of the base pipe.
 3. The screen pipe for thick oil thermalrecovery in horizontal well completion according to claim 1, wherein anouter wall of the wrap wire is coated with TiALN-WC/C coating.
 4. Thescreen pipe for thick oil thermal recovery in horizontal well completionaccording to claim 1, further comprising: a connector, wherein each oftwo ends of the base pipe is connected with a blind pipe through theconnector respectively.